1. Field of the Invention
This invention relates to a gas fired appliance simulating a log fire.
2. Review of the Art
Fireplace appliances fired by gas and which simulate a natural log or coal fire have long been known. In designing such appliances, particularly under modern conditions, two conflicting requirements must be reconciled. It is desirable to provide a simulation of a natural log fire which is as lifelike as possible, but at the same time to keep emissions of carbon monoxide as low as possible. Unfortunately, common methods of providing natural looking flame effects tend to result in incomplete combustion of the gas and thus increased carbon monoxide emissions.
Early examples of this type of appliance, typified by U.S. Pat. No. 263,255 issued to Verity in 1882 and U.S. Pat. No. 344,808 issued to Bradberry in 1886, utilise a perforated plenum fed with a gas/air mixture and covered with artificial coals of non-combustible material. The gas/air mixture necessarily contacts the coals before it is completely combusted, and the resulting cooling may readily result in incomplete combustion.
The problems discussed above were later recognized and are discussed in U.S. Pat. No. 3,291,116 issued to Brooks in 1966. Brooks points out that when conventional gas burners are used in a manner such as will achieve satisfactory combustion, the flames produced are small and of uniform height, making it impossible to obtain lifelike effects. Brooks' solution to this problem is to place his burner between transversely extending logs and surround it by an accelerator hood which induces flames which are said to be much higher and more natural looking. The arrangement requires rather careful design if it is to work properly, as acknowledged in column 4 of the Brooks patent, and is affected too greatly by variations in gas pressure to provide a safe and consistent solution to the problem of providing a natural looking flame effect.
U.S. Pat. No. 3,382,861, issued in 1968 to Peterson, also makes use of a burner hidden between two transverse logs. The burner has longitudinally elongated ports which appear to be fed with neat gas to provide a sheet flame which is deflected by air currents back against the rear log. Such an arrangement is likely to result in incomplete combustion, and it is not believed that it would meet the current standards applied by the American Gas Association.
U.S. Pat. No. 3,543,741, issued in 1970 to Whitehead, acknowledges the importance of allowing combustion to be substantially completed prior to any contact with the logs, and uses flame deflectors to achieve this. If such a deflector is to avoid cooling the burning gases so as to result in incomplete combustion, it must be able to reach and withstand very high temperatures. It is not apparent how the patentee achieves the large flame height shown in his drawings whilst achieving complete combustion.
U.S. Pat. No. 4,637,372 issued in 1987 to Mogol shows a further arrangement with a burner located between two transverse logs, but the burner is operated by liquid fuel and does not offer any teaching which would assist in resolving the problems set forth above.